shields



April 14, 1964 D. w. SHIELDS ARM BIASING CONSTRUCTION FOR RING TYPEDEBARKERS Filed Sept. 24, 1962 5 Sheets-Sheet l INVENTOR. .Dea-n LL}.Shields BY 2, 2 I fl x-Q H'b'tor-neys A ril 14, 1964 D. w. SHIELDS ARMBIASING CONSTRUCTION FOR RING TYPE DEBARKERS Filed Sept. 24, 1962INVENTOR. Dean S/lieIc/S BY 3 Sheets-Sheet 2 5.42 zf/YWM Hzzarn e 5United States Patent Ofiice Patented Apr. 14., 1964 3,128,805 ARMBIASING CGNSTRUCTION FOR RING TYPE DEBARKERS Dean W. Shields,Birmingham, A121,, assignor to Budow Manufacturing Company, Inc., acorporation of Alabama Filed Sept. 24, 1962, Ser. No. 225,634 Claims.(Cl. 144-408) This invention relates generally to ring type debarkersand specifically to means for urging the tool carrying arms toward thelog to be debarked.

In this art it is now known that it is desirable to urge the debarkingtools against the log with substantially constant pressure regardless ofthe size log being debarked. That is, during a given season of the yearand when debarking logs of a given species harvested in any given seasonof the year, such constant tool pressure is desirable. Since logs to bedebarked in a particular machine may vary in diameter from say 5 inchesto 30 inches, some means must be provided to compensate for such sizevariations, especially when the arms are loaded by springs. Generallyspeaking, spring systems exert varying forces depending upon the degreeof compression or tension thereof and this of course varies with eachlog diameter. In fact, the distance of the tools from the center of thering varies during the debarking of each log since logs are generallylarger at the butt ends than at the top ends. Further, it is imperativethat such arm loading mechanisms be simple, rugged and trouble-free andmost desirable that the system involve as few lubrication points andpivots as is possible.

In view of the foregoing the prime object of my invention is to providea tool arm loading system which accomplishes the objects and has theadvantages above mentioned.

Another object is to provide a spring system for each arm and totransmit the force of each spring system to its associated arm through aflexible member such as a cable, the cable passing over the outer end ornose of the arm which is so contoured that in all inner and outerpositions of the tool end of the arm, the effective force of the springurging the tool into contact with the log remains substantially constantthroughout the range of log sizes for which the debarker is designed.

A further object is to provide apparatus of the character designated inwhich the force of the spring system is transmitted directly to theouter end of the tool arm, eliminating various intermediate arms, linksand the like, and providing apparatus in which the force transmittingsystem itself is substantially unaffected by centrifugal force on theparts thereof as the debarker ring rotates.

A still further object is to so design the nose or outer end of the armaround which the flexible member passes as to compensate for the adverseeffect on constant tool force of the spring travel, the change ineifective moment arm due to rotation of the arm about its pivot, andcentrifugal force on the tool arm itself.

Apparatus illustrating features of my invention is shown in theaccompanying drawings forming a part hereof in which:

FIG. 1 is a front elevational view of the ring of a debarker having myimproved arm biasing means applied thereto, removed from the remainderof the debarker, partly broken away and in section;

FIG. 2 is an enlarged detail fragmental front elevational view withcertain parts broken away and in section;

FIG. 3 (sheet 1) is a slightly enlarged detail sectional view takengenerally along line 33 of FIG. 2;

FIG. 4 is a fragmental end elevational view of one of the debarking armslooking generally in the direction of the arrows 44 of FIG. 2;

FIG. 5 is a fragmental plan view of the end of one of the springhousings and the cross head for the ends of the flexible member thatextend around and under the outer ends of the debarker arms;

FIG. 6 is a graph plotting the relation between given angular positionsof one of the tool arms and centrifugal force on said arm;

FIG. 7 is a graph plotting the relation between the spring travel ininches and the force exerted by the spring in pounds;

FIG. 8 is a graph plotting the effective lever arm in inches against therotation of the arm in degrees starting at full open position; and,

FIG. 9 is a graph showing the relation between the tool movement ininches against the loading force on the tool in pounds, with the ringrotating at its designed speed.

Referring now to the drawings for a better understanding of my inventionI show at 10 the ring of a debarker which as Will be understood has anopening 11 therethrough through which the log to be debarked passes. Itwill be understood that the ring is mounted on suitable supports,bearings, trunnions or the like, not shown, for rotation in thedirection of arrow 12.

Mounted on one face, namely the front face, or in other words, the sideof the ring from which the log approaches, are a plurality of debarkerarms indicated generally by the numeral '13. Since each of the arms andits associated spring mechanism are identical, a description of one willsuffice for all. It will be understood that the debarker may be equippedwith three, five, or more arms.

Each of the arms 13 may be fabricated of plate members welded togetherand each may embody a hub 14. The hub 14 is mounted on the outer race 16of an antifriction bearing 17 (FIG. 3). The inner race 18 of the bearingis mounted on a pin 19 which may have a threaded outer end 21 receivinga lock nut 21*. The bearing may be sealed in the hub 14 by an oil seal22. The pin 19 may have an intermediate shoulder 24 and a rearward endsection 19 threaded to receive a lock nut 26. The pin 1? is supported ina suitable bushing 27 passing through the periphery of the ring whichwill be understood is made up of the plates 10 and 18 The entire ringmay be mounted for rotation on large diameter journal 10.

The arms are slightly spaced, on the order of, say, 20 thousandths inch,from wear plates 28 (FIG. 1) welded to the side of the ring. In normaloperation the wear plates are not contacted by the arms; however, shoulda log hit the ends of the arms head-on and deflect them toward the ring,the wear plates are contacted by the sides of the arms to prevent damageto the bearings and pins already described.

Mounted adjacent each arm, as by being welded to a bracket 29outstanding from the ring, is a spring housing in the form of a tubularmember 31. As best shown in FIG. 2, the spring housing is closed at itsforward end by a closure 32 and is open at its rear end 33. Also, theclosure 32 is provided with a vertically elongated opening 34.

Mounted in each of the housings 31 is a double coil compression spring36. The spring abuts at its upper end against an extension 32 spacedinwardly from the closure 32 and its outer end abuts a disc 37 having athreaded opening at its center.

Passing through the elongated opening 34 is a rod 38. The rod 38 isprovided with a threaded inner end 39 onto which the disc 37 is screwed.A lock nut 41 serves to hold the spring in adjusted position within itshousing as determined by the position of threaded disc or nut 37.

On the forward end of rod 38 is a cross head 42. Firmly secured insuitable openings in the cross head are the ends 43 and 44 of a cable45. The cable 45 passes around the nose or cam surface 13* of the arm,which later will be described, and the bight thereof passes under acleat 46 welded to the underside of the arm 13.

From what has been described it will be seen that the springs pullingthrough the cables 45 urge each of the arms inwardly so that the tools13 thereof are urged into contact with the log L to be debarked.Suitable stop means in the form of brackets 47 are provided for each armto limit inward movement of the tools.

lt is the shape or contour of the outer end or nose 13 of each arm, incombination with a flexible member such as the cables 45 to transmit theforce of the springs 36 thereto with which this invention isparticularly concerned.

Upon considering the position of the arms in FIG. 2 of the drawings, itwill be seen that the effective force of the springs urging the tool 13'inwardly is the force of the spring times the lever arm indicated at 48.It will further be understood that when the ring is rotating,centrifugal force acting through the center of mass of the lower part ofthe arms, indicated diagrammatically at 49, tends to move the tool 13away from the log. *Further, as the arms open outwardly, thereby tooperate upon a log of larger diameter than the one shown in FIG. 2, theeffective lever arm 48 decreases. Still further, as the tool ends of thearms move outwardly, further compressing the spring 36, the forceexerted by such spring increases. It is these three variables that Ihave been enabled to design out by the particular shape and contour ofthe nose or end 13 of the arm against which the flexible member bears.In other words, by shaping the surface which contacts the cable inpredetermined fashion, I can compensate for the increase in springpressure, the effect of centrifugal force, and the change in theefiective lever arm 48.

Referring now particularly to FIG. 6 of the drawings, I will firstdiscuss the effect of centrifugal force which tends to open the arms. Ina typical 30 inch debarker equipped with my invention and having armsheavy enough to do the job, the centrifugal force on the arms will startat nothing at zero rpm. and may increase to as much as 1040 pounds atthe design speed of, say, 75 rpm. of the ring. Therefore, oneconsideration of the shape or contour of the nose 13* is to make thelever arm 48 longer, in order to compensate for the opening effect onthe arms of centrifugal force.

Referring now to FIG. 7 it will be understood that the springs hereinvolved are considerably heavy springs, such for instance springs of anature in which the force may increase, starting with the arms in fullyclosed position, by as much as 600 pounds per inch of travel of the rod38 outwardly of the housing 31. Such springs may be compressed as muchas six inches. Therefore, such springs may exert a force of 2400 poundswhen the arms are fully closed, since they are pre-compressed forinitial loading and as much as 4800 pounds when the arms are fully open.

Referring now to FIG. 8 it will be seen that the effective lever arm 48,namely, a line normal to the center line of the cable and passingthrough the center of the pivot point, also varies due to simplerotation of the arm about its pivot point. Thus, for instance, in a 30inch debarker, and starting with the arms at fully open position andcalling this zero degrees rotation, it may be desirable for the leverarm 48 to be on the order of, say, 3 inches, and at fully closedposition on the order of, say, 4.4 inches.

In FIG. 9 I show the result which may be achieved by properly contouringthe nose or cable engaging outer end of the arm 13. Thus, the loadingforce on the tool, at the innermost position for the smallest log to bedebarked may be on the order of 320 pounds, depending upon the season ofthe year. It is desired that the tool loading force remain constant. Inother words, FIG. 9 of the drawings represents the sum total of thedesign which this invention affords, taking into account the variablesdiagrammatically illustrated in FIGS. 6, 7 and 8. By increasing theinitial tension on the springs, in the example given, I can increasethis constant tool loading force to, say 600 pounds; by decreasing it,in the example given, I can maintain this constant force, at say 240pounds.

The precise method of determining the shape of the cam or contouredportion 13 of the arms is as follows:

Having selected the spring 36 required to do the job and knowing thevariation in its force per linear inch of compression, knowing theeffective center of mass and the weight of the arm and the revolutionsper minute of the ring, knowing by layout the change in the effectivelever arm 48 for a tool arm of given length, having selected the lengthof the arm outwardly of the pivot point, by plotting the required forcesfor each degree of movement of the arm, I can arrive at the exact lengthof the effective lever arm 48 for each degree of rotation of the toolarm to maintain constant tool loading. Having arrived at these figuresit is a simple matter then to plot the exact shape of the nose or camportion 13.

It is to be especially noted that by so shaping the nose of the arm overwhich the cable passes, thus to keep the tool pressure force constantthroughout the range of log sizes for which the debarker is designed, Ihave eliminated a large number of linkages, pivots and the like. Myimproved arm biasing apparatus thus is simple, rugged, and fullyeffective.

While I have stated herein that the line indicating the effective toolforce in FIG. 9 is absolutely constant, it will be appreciated that theeffective force of gravity on the arms, in their several positions, isalso a variable. However, I have neglected taking this into account,first, because it is small, and second, because it does not affect theconstancy of the tool pressure more than one or two percent, which isnegligible.

In view of the foregoing it will be apparent that I have devised animproved means for urging or biasing debarker arms to their work, atsubstantially constant force throughout the entire range of log sizesfor which the debarker is designed. By passing the rod 38 through awasher 38 which may be of felt or other fibrous material, and which isfree to slide in the slot 38", and then by providing a closure for theend 33 of the housing 31, not shown, the springs are substantiallysealed in their housings. Sufiicient air can leak around the washer 38so that no part of the apparatus in the housing becomes a piston, thusto interfere with its movement.

It is to be noted that my improved arm urging or biasing system embodiesa minimum number of parts which are subject to centrifugal force whichwould have undesirable inertia. Therefore, the tools of a debarkerequipped with my improved system ride readily into and out ofdepressions, over knots and the like on the surfaces of the logs. Bysimply running in or out on the threaded washers or nuts 37, the toolloading force may be varied. In the illustration given it may beincreased to exert as much as 600 pounds on the tools, or as little asaround 200 pounds.

In actual practice debarkers equipped with my improved apparatus haveproved to be extremely satisfactory, trouble-free and rugged inoperation. As of the date of this application about fifteen debarkersthus equipped have been built and sold commercially. These have rangedin size from three arm, 24 inch debarkers, to five arm, 38 inchdebarkers. By using a double tapered roller hearing as shown in FIG. 3,I am enabled to seal the bearings, maintaining them always welllubricated, thus to increase the trouble-free operation of theapparatus.

While I have shown my invention in but one form, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various changes and modifications without departing from the spiritthereof, and I desire, therefore, that only such limitations shall beplaced thereupon as are specifically set forth in the appended claims.

What I claim is:

l. The combination with the ring of a ring type debarker,

(a) of a tool carrying arm pivotally mounted intermediate its ends on aside of the ring,

(b) a spring abutment for a compression spring mounted on the ringadjacent the pivot point of the arm,

() a compression spring having one end resting against the abutment,

(d) a cross head in contact with the opposite end of the spring,

(e) a flexible member operatively connected at one end to the cross headand with its other end passing loosely around at least a portion of theouter end of the arm and secured to the arm,

(1) and the surface of the outer end of the arm engaged by the flexiblemember being so contoured that the resultant force of the spring urgingthe tool toward the center of the ring remains substantially constantthroughout the range of inner and outer movement of the tool carryingend of the arm.

2. The combination with the ring of a ring type debarker,

(a) of an arm pivoted intermediate its ends to a side of the ring andhaving a debarking tool on its inner end,

(b) an abutment for a compression spring mounted on said side of thering adjacent said pivot point,

(0) a compression spring having one end resting against the abutment,

(d) a flexible member operatively connected at one end to the ends ofthe spring opposite the abutment and passing loosely over at least aportion of the end of the arm outwardly of the pivot point thereof,

(e) means securing the flexible member to the arm at a point thereonremoved from the portion thereof over which the flexible member looselypasses, and

(f) the portion of the end of the arm loosely engaged by the flexiblemember being so contoured that as the arm moves from closed position toopen position, thus to compress the spring, the effective lever armthrough which the spring acts on the debarker arm decreases, thereby toload the tools substantially constantly throughout the range of logsizes for which the debarker is designed.

3. For use in a ring type debarker,

(a) a tool arm pivoted intermediate its inner and outer ends anddisposed to carry a debarking tool on its inner end,

(b) a spring for the arm characterized in that the force deliveredthereby varies with its travel,

(0) a flexible member operatively connected to transmit the force ofsaid spring to the arm, and

(d) a contoured section on the arm outwardly of its pivot point overwhich the cable passes in unattached manner, the cable being secured tothe arm at a point other than in said contoured section thereof, theconfiguration of said contoured section being such as to compensate forthe change in force exerted by the spring and for the change ineffective lever arm through which the force thereof is applied to saidarm, whereby the tool is urged against logs of varying diameter withsubstantially constant force.

4. Apparatus as defined in claim 3 in which the configuration of saidcontoured part of the arm also is constructed and arranged to compensateat least in part for the opening effect on the arms of centrifugal forceto which the arm is subjected when in place on the ring of a debarker.

5. Apparatus as defined in claim 3 in which,

(a) the spring is a compression spring,

(b) and in which the flexible member is a length of cable or the likedoubled back upon itself with the bight thereof secured to the arm andthe free ends thereof operatively connected to the spring in a fashionto transmit compressive force thereof to the arms through the flexiblemember.

References Cited in the file of this patent UNITED STATES PATENTS2,786,499 Brundell et a1 Mar. 26, 1957 2,897,859 Annis Aug. 4, 19593,058,500 Smith Oct. 16, 1962

3. FOR USE IN A RING TYPE DEBARKER, (A) A TOOL ARM PIVOTED INTERMEDIATEITS INNER AND OUTER ENDS AND DISPOSED TO CARRY A DEBARKING TOOL ON ITSINNER END, (B) A SPRING FOR THE ARM CHARACTERIZED IN THAT THE FORCEDELIVERED THEREBY VARIES WITH ITS TRAVEL, (C) A FLEXIBLE MEMBEROPERATIVELY CONNECTED TO TRANSMIT THE FORCE OF SAID SPRING TO THE ARM,AND (D) A CONTOURED SECTION ON THE ARM OUTWARDLY OF ITS PIVOT POINT OVERWHICH THE CABLE PASSES IN UNATTACHED MANNER, THE CABLE BEING SECURED TOTHE ARM AT A POINT OTHER THAN IN SAID CONTOURED SECTION THEREOF, THECONFIGURATION OF SAID CONTOURED SECTION BEING SUCH AS TO COMPENSATE FORTHE CHANGE IN FORCE EXERTED BY THE SPRING AND FOR THE CHANGE INEFFECTIVE LEVER ARM THROUGH WHICH THE FORCE THEREOF IS APPLIED TO SAIDARM, WHEREBY THE TOOL IS URGED AGAINST LOGS OF VARYING DIAMETER WITHSUBSTANTIALLY CONSTANT FORCE.